The fabrication of wheel shaped composite gears and sprockets including a combination of a grey iron hub surrounded by an outer annulus of a softer, machinable material, such as plastic or bronze, extending from the outer surface of the hub is generally known. The provision of a grey iron hub for such a composite gear provides a hard material that is suitable for many applications. Grey iron is not as suitable as other materials for use as the outer portion of a gear having precisely formed gear teeth because it is relatively brittle and does not intermesh well with an opposing gear and can corrode. Nevertheless, the use of iron substantially reduces the cost of the composite gear if compared to the cost of a gear made entirely of a standard gear outer portion material such as bronze. Also, provision of a bronze annulus cast onto the hub is desirable because bronze does not easily corrode and forms well with an intermeshing gear. The use of a casting method to interconnect a hub and surrounding annulus, rather than other mechanical methods of interconnecting, is known and desirable as an efficient method to interconnect the hub and annulus.
In such composite gears, the outer annulus of bronze is typically cast onto the hub such that it surrounds the peripheral surface of the hub. The annulus is securely fixed to the hub through the mechanical bond that is created due to the circular, or surrounding nature of the annulus in relation to the hub. The annulus is held on the hub through the mechanical bond that is formed between the hub and the annulus due to the fact that the annulus surrounds the hub.
Sector gears, or quadrant gears, are gears that resemble a portion of a wheel shaped gear containing the hub and only a portion of the outer annulus. The annulus of a sector gear does not completely surround the peripheral surface of the hub. Sector gears in which the annulus and the hub are made of a single material are generally known. Composite sector gears wherein the annulus is made of a different material from the hub can be produced by attaching the annulus to the hub with bolts or screws, but such methods of production are very inefficient.